The proposed study tests the hypothesis that relationship qualities in adolescence ultimately have substantial implications for two important domains of adult physical health: cardiovascular health and metabolic functioning. We address these questions using repeated assessments with multi-reporter, multi-method data from a demographically diverse final sample of 172 individuals followed from age 13 to 32. We focus on two key social relationship pathways that we hypothesize to have substantial long-term physical health ramifications: 1. from the adolescent struggle to establish autonomy adaptively when negotiating disagreements to hostile conflict in future relationships; and, 2. from failure to establish supportive social connections in family and peer relationships to future social isolation We will pursue the following aims: Aim 1: Direct Prediction of Adult Health Indicators from Adolescent Relationship Characteristics We begin with the most basic, yet important epidemiological task of seeking to identify adolescent relational qualities that may directly predict substantial future risks for long-term health difficulties. Aim 2: Intervening Psychosocia Mediators of Links from Adolescence to Adult Health - After identifying key adolescent psychosocial risk factors, we next examine the hypothesized intervening pathways that may explain these risks and can thus suggest further potential arenas for intervention. To properly temporally assess these mediated pathways, we assess direct predictions from adolescence to adult social functioning and cross-lagged predictions between social functioning and health outcomes in adulthood. Aim 3: The Role of Temporal and Contextual Effects - We next seek to distinguish the long-term effects of chronic vs. intermittent social functioning difficulties (e.g. are there lingering effects when a prior pattern of social isolation or hostile conflict eventually resolves?) as well as considering the mediating and moderating roles of key contextual transitions and demographic factors. Aim 4: Interplay of Relational Functioning, Mental Health, and Physical Health - Finally, we assess the interplay of social functioning and mental health in predicting physical health outcomes both from adolescence to adulthood and within adulthood, considering both unique and conjoint effects of relational factors and mental health symptoms as they work together to predict health outcomes. Overall, the proposed study has the potential: a. to open up an entirely new arena for potential screening tools and preventive interventions to improve lifelong health outcomes and suggest specific relational characteristics to target; b. to provide guidance to parents, educators, and clinicians seeking to distinguish transient adolescent relationship difficulties from difficulties with greatest long-term import for health; ad c. to dramatically advance developing theories of the link between adolescent social relationship qualities and major health outcomes into this critical, relatively unexplored portion of the lifespan.